Reading disability (RD or dyslexia) is characterized by deficits in word recognition and decoding. While much is understood about the neurobiological and behavioral characteristics, natural history and intervention for dyslexia in young children, less is understood about adults with dyslexia. While studies have found that adult dyslexia is characterized by behavioral deficits similar to those found in children (poor phonological processing and inaccurate and slow word recognition) less is understood about the underlying neurobiological characteristics. While some functional neuroimaging studies of adults with dyslexia show results similar to those patterns of abnormalities found in children with RD, others have shown quite different patterns of activation. This variability could be due to greater heterogeneity of the expression and/or compensatory changes associated with dyslexia among older readers. This heterogeneity might manifest as differences in etiology and/or location of the "affected" brain tissue, which might be detectable in local white matter microstructure and/or neurochemical environment. To date, little work has been done examining the underlying white matter pathways or the potential neurochemical abnormalities in young adults with dyslexia, which is the first goal of this project. A second goal of this project is to conduct a finer-grained examination of functional brain activation differences in young adults with and without dyslexia by use of a repetition paradigm. Repetition of word stimuli is a well established behavioral manipulation that facilitates recognition of the repeated words (i.e., learning) and recently has been shown to correlate with consolidation of fMRI activation in the left perisylvian area. This project proposes to use a fMRI repetition paradigm to examine whether adults with dyslexia may demonstrate differential brain responses to repetition, and how these differential responses may be related to white matter microstructural and/or neurochemical abnormalities. In short, the goal of this project is to provide further understanding of the neurobiological correlates of adult dyslexia, with a particular focus on understanding the neurochemical and structural (white matter pathway) characteristics, and how these differences may be associated with cortical response to learning. PUBLIC HEALTH RELEVANCE: Our technologically advanced society requires some post-secondary education for employment. Approximately one third of young adults are functioning at a level of literacy that is unlikely to be adequate for future education as well as employment settings. The proposed project focuses on understanding more about the neurobiological characteristics of adults who are struggling readers, which is critical to understand more about the etiology of struggling readers and to help inform evidence-based instruction.